Description:
------------
The memory leak occurs when 
- ZipArchive is opened with ZipArchive::CREATE|ZipArchive::OVERWRITE flags, 
- it's empty,
- it's destroyed without explicit close() method call.

The leak does not occur if zip-file already exist. 

All PHP versions are affected. 

Test script:
---------------
$zip = new ZipArchive();
$zip->open(__DIR__.'/nonexistent.zip', ZipArchive::CREATE | ZipArchive::OVERWRITE);

Expected result:
----------------
Done
Warning: Unknown: Cannot destroy the zip context in Unknown on line 0

Actual result:
--------------
Done
Warning: Unknown: Cannot destroy the zip context in Unknown on line 0
[Sun Jun 24 20:52:32 2018]  Script:  '...'
/.../php-src/ext/zip/php_zip.c(1141) :  Freeing 0x7FED6E9998B8 (80 bytes), script=...
[Sun Jun 24 20:52:32 2018]  Script:  '...'
/.../php-src/main/fopen_wrappers.c(808) :  Freeing 0x7FED6E99A090 (41 bytes), script=...
=== Total 2 memory leaks detected ===